Code:
     +-------+
     | marks |
     |-------|
  1. |    21 |
  2. |    20 |
  3. |    15 |
  4. |  33*‡ |
  5. |    16 |
     |-------|
  6. |    16 |
  7. |    29 |
  8. |  36*‡ |
  9. |  30*‡ |
 10. |       |
     |-------|
 11. | 13**† |
 12. | 13**† |
     +-------+
I would like to destring the variable marks and generate a new variable, say, note, which would contain the symbols "*" and "‡". For example, the new variable, note,will have "*‡" for observation 4; "**†" for observation 11.

Code:
* Example generated by -dataex-. To install: ssc install dataex
clear
input str7 marks
"21"     
"20"     
"15"     
"33*‡" 
"16"     
"16"     
"29"     
"36*‡" 
"30*‡" 
""       
"13**†"
"13**†"
end